Investigating the mapping of chromophore excitations onto the electron detachment spectrum: photodissociation spectroscopy of iodide ion–thiouracil clusters

Abstract

Near threshold photoexcitation of iodide–thiouracil clusters explores the coupling of nucleobase centred excitations onto the electron detachment spectrum.

Photostability of the deprotonated forms of the UV filters homosalate and octyl salicylate: molecular dissociation versus electron detachment following UV excitation

“…54,55 Below the electron detachment energy, photoexcitation can only access valence excited states, which can decay radiatively or through dissociation into an anionic and neutral fragment pair. Above the detachment energy, electronic excited states are coupled to the electron detachment continuum, 56 and can thus be considered autodetaching resonances. Electron detachment can either occur directly from the excited state or following excited state decay back to the ground electronic state and ensuing thermionic emission.…”

Action Plots in Action: In-Depth Insights into Photochemical Reactivity

“…Within the field of photochemistry, action spectra have been primarily limited to photodissociation studies, where a monochromatic light source, usually a laser, is coupled to a mass spectrometer and the wavelength-dependent dissociation of ions in the gaseous phase is recorded . As with biological studies, photodissociation action spectra have been utilized to identify the contributing chromophore in molecular systems, , in addition to characterizing radical generation and unstable isomers − and understanding higher state electron dynamics. , …”

Effect of Freezing out Vibrational Modes on Gas-Phase Fluorescence Spectra of Small Ionic Dyes

“…The development of electrospray ionization (ESI) in combination with mass spectrometry by Fenn and co-workers in the 1980s made it possible to bring large and fragile molecular ions intact into the gas phase and measure their mass-to-charge ratios. This paved the way for gas-phase spectroscopy of previously inaccessible ions such as ionic protein biochromophores, nucleobases, and (oligo)­nucleotides. − Nevertheless, gas-phase absorption or fluorescence experiments are still challenging due to low target ion concentration, and absorption is only detected indirectly from dissociation, electron detachment, or photon emission, so-called action spectroscopy. , In the case of fluorescence spectroscopy, − it is crucial to lower the background of scattered photons from the incoming laser light, and sample as many of the emitted photons as possible. Initially, action spectra were recorded at room temperature, but buffer-gas cooling in multipole or quadrupole ion traps is now a well-established technique to provide cryogenic cold ions and as a result much less congested spectra. − At low temperatures, it is also possible to tag ions with noble gas atoms or molecular hydrogen or nitrogen with the obvious advantage that loss of the tag provides a low-energy dissociation channel for action spectroscopy. − This solves the inherent problem of dissociation for molecular ions with many degrees of freedom or high dissociation barriers.…”